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BMC Genomics. 2009; 10: 111.
Published online Mar 16, 2009. doi:  10.1186/1471-2164-10-111
PMCID: PMC2662880
Population-specific gene expression in the plant pathogenic nematode Heterodera glycines exists prior to infection and during the onset of a resistant or susceptible reaction in the roots of the Glycine max genotype Peking
Vincent P Klink,corresponding author#1,2 Parsa Hosseini,#3 Margaret H MacDonald,2 Nadim W Alkharouf,3 and Benjamin F Matthews2
1Department of Biological Sciences, Harned Hall, Mississippi State University, Mississippi State, MS 39762, USA
2United States Department of Agriculture, Plant Sciences Institute, Beltsville, MD 20705, USA
3Jess and Mildred Fisher College of Science and Mathematics, Department of Computer and Information Sciences, Towson University, 7800 York Road, Towson, Maryland 21252, USA
corresponding authorCorresponding author.
#Contributed equally.
Vincent P Klink: vklink/at/biology.msstate.edu; Parsa Hosseini: phosse1/at/towson.edu; Margaret H MacDonald: Margaret.MacDonald/at/ARS.USDA.GOV; Nadim W Alkharouf: nalkharouf/at/gmail.com; Benjamin F Matthews: Ben.Matthews/at/ARS.USDA.GOV
Received August 29, 2008; Accepted March 16, 2009.
Abstract
Background
A single Glycine max (soybean) genotype (Peking) reacts differently to two different populations of Heterodera glycines (soybean cyst nematode) within the first twelve hours of infection during resistant (R) and susceptible (S) reactions. This suggested that H. glycines has population-specific gene expression signatures. A microarray analysis of 7539 probe sets representing 7431 transcripts on the Affymetrix® soybean GeneChip® were used to identify population-specific gene expression signatures in pre-infective second stage larva (pi-L2) prior to their infection of Peking. Other analyses focused on the infective L2 at 12hours post infection (i-L212h), and the infective sedentary stages at 3days post infection (i-L23d) and 8days post infection (i-L2/L38d).
Results
Differential expression and false discovery rate (FDR) analyses comparing populations of pi-L2 (i.e., incompatible population, NL1-RHg to compatible population, TN8) identified 71 genes that were induced in NL1-RHg as compared to TN8. These genes included putative gland protein G23G12, putative esophageal gland protein Hgg-20 and arginine kinase. The comparative analysis of pi-L2 identified 44 genes that were suppressed in NL1-RHg as compared to TN8. These genes included a different Hgg-20 gene, an EXPB1 protein and a cuticular collagen. By 12 h, there were 7 induced genes and 0 suppressed genes in NL1-RHg. By 3d, there were 9 induced and 10 suppressed genes in NL1-RHg. Substantial changes in gene expression became evident subsequently. At 8d there were 13 induced genes in NL1-RHg. This included putative gland protein G20E03, ubiquitin extension protein, putative gland protein G30C02 and β-1,4 endoglucanase. However, 1668 genes were found to be suppressed in NL1-RHg. These genes included steroid alpha reductase, serine proteinase and a collagen protein.
Conclusion
These analyses identify a genetic expression signature for these two populations both prior to and subsequently as they undergo an R or S reaction. The identification of genes like steroid alpha reductase and serine proteinase that are involved in feeding and nutritional uptake as being highly suppressed during the R response at 8d may indicate genes that the plant is targeting. The analyses also identified numerous putative parasitism genes that are differentially expressed. The 1668 genes that are suppressed in NL1-RHg, and hence induced in TN8 may represent genes that are important during the parasitic stages of H. glycines development. The potential for different arrays of putative parasitism genes to be expressed in different nematode populations may indicate how H. glycines evolve mechanisms to overcome resistance.
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